Nuclear imaging is an effective way of dagnosing cardiovascular disease. It shows not only the structure of the heart, but its function as well. By acquiring images of the heart’s pump action and blood flow, nuclear imaging can detect the presence of cardiovascular disease much sooner than methods that provide only structural information.
There are two applications of nuclear imaging in cardiology:
- Perfusion Imaging: The examination of blood flow to the heart muscle.
- Dynamic Imaging: The examination of your heart muscle’s function (how well it pumps).
Perfusion studies use Technetium-99m to acquire images of the heart. Dynamic studies, which include radionuclide angiography (RNA or First Pass), use the same radioisotope, but apply a different technique to acquire images.
While each study is intended to yield very specialized and differing information, both perfusion and dynamic imaging share common characteristics:
- The tests are performed on an outpatient basis, so hospitalization is not required.
- Nuclear cardiology studies are quite safe, rarely accompanied by complications.
- Your heart rate and rhythm are closely monitored during and after stress by electrodes on your chest which are connected to an ECG monitor.
- Both techniques require the injection of a small amount of radioactive material, called an “isotope,” into one of your veins. The small amount of radionuclide which you receive is eliminated from your body in one or two days.
- Both use a gamma camera to record images of your heart. The camera does not produce radiation.
- You are not permitted to eat or drink anything after midnight before the stress portion of the study. This prevents nausea during exercise and allows better uptake of the radioactive isotope by your heart.
Perfusion Imaging Study (Technetium-99m Imaging)
These nuclear studies are used to test for America’s most common cardiovascular problem — coronary artery disease. This disease affects the arteries that supply blood to the heart muscle. When blockage or restriction in the coronary arteries reduces the flow of blood and oxygen to the heart muscle, symptoms such as chest pressure, tightness, heaviness, and discomfort in the arm, jaw, back or neck are produced (commonly referred to as “angina pectoris”). Other, less noticeable symptoms may include shortness of breath or fatigue.
A nuclear perfusion study can detect partial or complete coronary artery blockages with significant accuracy.
Reasons for Ordering Perfusion Study
There are several reasons for ordering a nuclear cardiology perfusion study:
- When angina symptoms are present, the test reliably indicates presence or absence of significant coronary artery blockage
- To verify the findings of a simple stress test
- Once a heart catheterization has revealed a partial blockage, the perfusion study can determine if the blockage is contributing to symptoms of angina or if it is benign
- To determine the degree of success of coronary bypass surgery and reassess the bypass on an on-going basis
- When an electrocardiogram is abnormal but there are no other symptoms, the perfusion studies will determine if coronary artery disease is present
- To evaluate the immediate and later success of the coronary and angioplasty (PTCA) procedure
What Your Can Expect During a Perfusion Study
Be sure to arrive for the test early or on time. The study consists of two phases. During the first phase, a small intravenous line (IV) will be placed in your arm and the treadmill exam will begin. Once you have reached a predetermined maximum heart rate or feel that you cannot continue more than one minute on the treadmill, a small amount of the radioactive isotope will be injected through the IV. The radioisotope travels through the blood vessels to the heart muscle. Your cardiologist will be present for this portion of the test. Next, you are placed in a supine position beneath a camera, which records images of your heart. You can expect to be in our office for another 1 to 1-1/2 hours for the first phase.
The second phase, which records images of your heart at rest, will be scheduled when the first phase has been completed. You can expect to be in our office for another 1 to 1-1/2 hours for the second phase.
Data from the two scans are fed into a computer for analysis and reviewed by a physician with special knowledge in cardiology and nuclear medicine.
Perfusion Study Results
Your physician or his assistant will call you with the results within a few days following the test. In cases where the physician wants to discuss the results with you in person, the office will call you to schedule an appointment.
Dynamic Imaging Study
Left undetected or unremedied, a coronary artery blockage can result in a myocardial infarction or heart attack. Such an event may cause a portion of the heart muscle to die, decreasing the heart’s ability to pump effectively.
Dynamic imaging studies allow careful evaluation of the heart’s pumping chambers to determine their efficiency. These studies can detect inefficient heart function due to leaky or stiff heart valves. The Heart Institute of Venice performs radionuclide angiocardiography (RNA) along with the second half of the test.
What You Can Expect During a Dynamic Imaging Study
Be sure to arrive early or on time for your appointment. Before the procedure begins, an IV line will be started in your arm.
An RNA (commonly referred to as a “First Pass”) is performed while lying down beneath a gamma camera. After careful positioning, a small amount (<1ml) of the isotope is rapidly injected into the IV, which is followed by a ‘flushing’ injection of saline. The camera will image the path of the isotope as it traverses the heart during its first pass. Information about the heart’s output and ventricular function can be evaluated.
Allow 1 to 1-1/2 hours in our office. This time frame includes the second portion of the stress test.
Dynamic Study Results
Results are generally available a day or two following your test. Your cardiologist will review the findings with you at that time. Additional tests or treatments may be discussed, as well as the subsequent need for reevaluations at a later date.
If You Can’t Walk on a Treadmill
If a patient can’t walk on a treadmill, we have pharmacologic methods of stressing the heart using one of two drugs, Persantine or Dobutamine. Your cardioloist will determine which drug to use based on individual requirements.